Consider the NAT scenario shown in the figure below. Suppose that host 10.0.0.2
ID: 3700688 • Letter: C
Question
Consider the NAT scenario shown in the figure below. Suppose that host 10.0.0.2 initiates a connection, using source port 5500 to a Web server listening at port 80 at 128.119.40.186. rest of Internet local network (e.g., home network) 10.0.0/24 10.0.0.1 10.0.0.4 10.0.0.2 138.76.29.7 10.0.0.3 a. Complete the NAT translation table for this TCP connection. b. What are the source and destination IP addresses and port numbers on the IP datagram arriving to the WAN side of the router with interface address 138.76.29.7?Explanation / Answer
Answer:
Network address translation provides a single source NAT IP address to datagrams leaving the local network with different port numbers.
a. As given in the question that host 10.0.0.2 initiates a connection at port 5500 to reach to a web server listening at port 80 at 128.119.40.186, so the NAT table for this scenario will be as follows:
After reaching the destination web server at 128.119.40.186, the reply will be sent to 138.76.29.7, 5001 and then NAT router will change the datagram destination address from 138.76.29.7, 5001 to 10.0.0.2, 5500 .
b. The source Ip addresses arriving at WAN side of the router with interface address 138.76.29.7 will be same as 138.76.29.7 but the port numbers will change when reaching the destination.
And while coming back from destination web server, the source IP address will be that of the web server that is, 128.119.40.186, 80 and the destination Ip address will be of the WAN side router i.e., 138.76.29.7, 5001 for host 10.0.0.2, 5500 and 138.76.29.7, 5002 for host 10.0.0.1, 5501 and 138.76.29.7, 5003 for host 10.0.0.3, 5502.
Private Ip Address &port Public Ip Address & port 10.0.0.2, 5500 138.76.29.7, 5001 10.0.0.1, 5501 138.76.29.7, 5002 10.0.0.3, 5502 138.76.29.7, 5003Related Questions
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